Star forming regions linked to RCW78 and the discovery of a new IR bubble

Aims. With the aim of investigating the presence of molecular and dust clumps linked to two star forming regions identified in theexpanding molecular envelope of the stellar wind bubble RCW78, we analyzed the distribution of the molecular gas and cold dust.Methods. To accomplish this study we performed dust continuum observations at 870 μm and 13CO2–1 line observations with theAtacama Pathfinder EXperiment APEX telescope, using the Large Apex BOlometer CAmera LABOCA and SHeFI-1 instruments,respectively, and analyzed Herschel images at 70, 160, 250, 350, and 500 μm.Results. These observations allowed us to identify cold dust clumps linked to region B that we have named the southern clumpand region C clumps 1 and 2, and an elongated filament. Molecular gas was clearly detected linked to the southern clump and thefilament. The velocity of the molecular gas is compatible with the location of the dense gas in the expanding envelope of RCW78.Weestimate dust temperatures and total masses for the dust condensations from the emissions at different wavelengths in the far-IR andfrom the molecular line using local thermodynamic equilibrium and the virial theorem. Masses obtained through different methodsagree within a factor of 2–6. Color–color diagrams and spectral energy distribution analysis of young stellar objects YSOs confirmedthe presence of intermediate and low-mass YSOs in the dust regions, indicating that moderate star formation is present. In particular,a cluster of IR sources was identified inside the southern clump. The IRAC image at 8 μm revealed the existence of an infrared dustbubble of 16 in radius probably linked to the O-type star HD117797 located at 4 kpc. The distribution of the near- and mid-IR emission indicate that warm dust is associated with the bubble.Nota general